Password aging (or password rotation) is a policy that forces users to change their passwords after a defined time period passes, such as every 30 or 90 days. A long expiration provides more time for attackers to conduct password cracking before users are forced to change to a new password. Note that while password aging was once considered an important security feature, it has since fallen out of favor by many, because it is not as effective against modern threats compared to other mechanisms such as slow hashes.

In addition, forcing frequent changes can unintentionally encourage users to select less-secure passwords. However, password aging is still in use due to factors such as compliance requirements, e.g., Payment Card Industry Data Security Standard (PCI DSS).